Circuit breaker mechanism and method for assembly and loading of the operating spring



Feb. 15, 1966 w. w. POULTON, JR 3,235,689 CIRCUIT BREAKER MECHANISM AND METHOD FOR ASSEMBLY AND LOADING OF THE OPERATING SPRING Filed Aug. 17, 1961 3 Sheets-Sheet 1 INVENTOR. /(//1 MN w P001 70, MA.

Feb. 15, 1966 POULTON, JR 3 235,689

. W. CIRCUIT BREAKER MECHANISM AND METHOD FOR ASSEMBLY AND LOADING OF THE OPERATING SPRING Filed Aug. 17, 1961 5 Sheets-Sheet 2 Feb. 15, 1966 w. POULTON, JR 3,535,689

CIRCUIT BREAKER MECHANISM AND METHOD FOR ASSEMBL Filed Aug. 17, 1961 AND LOADING OF THE OPERATING SPRING 3 Sheets-Sheet 3 United States Patent 3,235,689 CIRCUIT BREAKER MECHANISM AND METHOD FOR ASSEMBLY AND LOADING OF THE OPER- ATING SPRING Wilson Poulton, Jr., Broomall, Pa., assignor to I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Filed Aug. 17, 1961, Ser. No. 132,046 6 Claims. (Cl. 200-116) This application relates to circuit breakers in general and more particularly to a simplified procedure for assembling the circuit breaker operating mechanism.

In a typical molded case circuit breaker having quick make and quick break features the operating mechanism thereof is provided with a spring for moving the contacts into and out of engagement. Whether the contacts are engaged or disengaged the springs must be loaded. That is, these springs furnish the required contact pressure to maintain the contacts closed when the circuit breaker is on, and when the circuit breaker is off these springs prevent unwanted movement of the contacts toward engagement.

As the circuit breaker art has progressed designs have been improved to a point where circuit breakers of very high interrupting capacities are of compact construction.

The high capacities and compact construction requires that the operating springs though small in size be very strong. In addition, the operating springs are usually positioned in extremely cramped quarters.

Because of the cramped conditions in the region of the springs and strength of the springs, loading thereof has been very diflicult. That is, in the prior art it was necessary to load the springs prior to final assembly of the operating mechanism links to the frame. Loading was accomplished by means of a drift pin which it was necessary to remove during one of the final assembly operations.

This invention overcomes the difficulty of prior art manufacturing by providing an assembly procedure in which the operating mechanism is completely assembled in the free state. Thereafter, loading of the operating springs is accomplished merely by moving the operating handle extension relative to the frame and inserting bushings on the bearing pins extending outboard from the frame which serve as pivots for the operating handle extension. When the operating handle extension is released the operating springs drive the handle extension toward the bearings but the bushings limit this movement so that the springs remain loaded.

Accordingly, a primary object of this invention is to provide a novel procedure for the assembly of a circuit breaker operating mechanism.

Another object is to provide a procedure for assembling an operating mechanism in which the loading of the operating springs is one of the last operations.

Still another object is to provide an assembly procedure for a circuit breaker operating mechanism in which the mechanism is completely assembled in the free state and thereafter the operating springs are loaded.

A further object is to provide a circuit breaker operating mechanism in which the handle extension is pivotally supported on bushings of a thickness such that when the bushings are removed the operating springs will be unloaded.

These as well as further objects of this invention shall become readily apparent after reading the following description of the accompanying drawings in which:

FIGURE 1 is a perspective of a molded case circuit breaker constructed in accordance with the teachings of the instant invention. In FIGURE 1 the cover is re- 3,235,689 Patented Feb. 15, 1966 moved to reveal the internal mechanism of the circuit breaker.

FIGURE 2 is a longitudinal cross-section of the circuit breaker of FIGURE 1 illustrating the current path through the circuit breaker.

FIGURE 3 is an exploded perspective of the circuit breaker operating mechanism.

FIGURE 4 is a cross-section of the pivot for the manual operating handle extension.

FIGURES 5-7 are side elevations illustrating the relationship between the handle extension and its pivot during various stages of assembly. In FIGURE 5 the contact operating springs are relaxed, in FIGURE 6 the springs are loaded for the assembly operation, and in FIGURE 7 the springs are still loaded with the handle extension in final operating position resting upon its pivot.

Now referring to the figures and more particularly to FIGURES 1 and 2 which illustrate a circuit breaker constructed in accordance with the teachings of the instant invention. The copending application 108,812, now Patent No. 3,155,802, filed May 9, 1961, of E. R. Wortmann,titled U-Shaped Cradle for Circuit Breaker, and assigned to the assignee of the instant invention, describes the circuit breaker in much greater detail than is required for purposes of this application.

Briefly, circuit breaker 10 is provided with a molded insulating housing comprising base 11 and removable cover 12 joined along line 13. Circuit breaker 10 is a three-phase unit so that base 11 is divided intothree parallel compartments by partitions 14 and 15. Each of the parallel compartments houses the current carrying members, for the respective phases. Since each phase is comprised of identical current carrying parts of the center phase will be described.

These current carrying parts comprise load terminal connector 16, load terminal 17, the looped extension 18 thereof extending through instantaneous trip magnet 19, through a portion 20 of terminal 17 having a reduced cross-section so as to serve as an indirect heater for bimetal time delay tripping element 21. The current path continues through conductor 22, flexible braid 23, movable contact arm 24 and movable contact 25 to stationary contact 26 which is mounted upon line terminal strap 27, having tulip line terminal connector 28 mounted thereto by screw means 29.

The movable contacts 25 of all three phases are operated simultaneously into and out of engagement with their respective stationary contacts 26 by means of a single operating mechanism 30 which is positioned in the center compartment. Each of the movable contact arms 24 is pivotally mounted at 31 to its individual U- shaped holder 32 between the arms thereof. Each holder 32 is provided with a portion 33 which defines a rectangular opening having insulating tie rod 34 disposed therein. Tie rod 34 extends through all three housing compartments so that the contact arm holders 32 of all three phases are mounted thereto. It is clearly seen that movement of tie rod 34 brings about the simultaneous movement of all three contact arms 24.

Leaf spring 37, fixedly mounted to holder 32 by rivet 38, acts upon adjusting screw 39 to urge contact arm 24 in a counterclockwise direction with respect to FIGURE 3 toward engagement with holder surface 40. As clearly shown in FIGURE 2, when contacts 25, 26 are in engagement, contact arm 24 is spaced from holder surface 40. In the outer two phases, screw means 41 secures load terminal member 17, conductor 22 and a cooperating bracket (not shown) to base 11, as illustrated in aforementioned copending US. Patent application Serial No. 108,812. In the center phase screw means 41 secures 3 load terminal strap 17, conductor 22 and mechanism frame 42 to base 11.

Frame 42 is a somewhat U-shaped member having pins 43 extending outwardly from the arms thereof. Operating member 45, which is eifectively an extension of handle 49, straddles frame 42 with pins 43 being disposed within the open ended slots 44 at the lower end (with respect to FIGURE l) of operating member 45. Manual operating handle 49 is mounted at the upper end of member 45 and includes a portion extending externally of housing 11, 12 through aperture 50 in cover 12. Spring 51, interposed between member 45 and handle 49 biases a portion of handle 49 against the inner surface of cover 12.

Intermediate latch member 46 is pivotally mounted on shaft 47 whose ends are guided by elongated slots 48 in the load end of frame 42. Spring 52, interposed between frame 42 and latch member 46, biases latch member 46 counterclockwise about pivot 47 toward latching position. Latch extension 53 of member 46 extends toward the breaker load end and is engageable with latch plate 54 carried by common tripper bar 55.

Bar 55 is an insulating member extending across all three base compartments being pivotally mounted at the ends thereof to uprights 56. Tension spring 57 biases bar 55 counterclockwise to latching position which is established through its engagement with adjusting screw 58 threadably mounted to one of the uprights 56.

Operating mechanism 30 also includes cradle 60, a toggle linkage comprising links 62, 63, and operating spring means 64, 65. As best seen in FIGURE 3, cradle 60 is a generally U-shaped member whose web 61 faces the load end of circuit breaker when cradle 66 is in latched position as in FIGURE 2. Cradle 60 is maintained in this position through the engagement of latch plate 66, mounted to web 61, With the web 67 of intermediate latch member 46, whose extension 53 is in engagement with latch plate 54, carried by tripper bar 55. Cradle 60' is biased to its tripped position by spring means 64, 65, as will become evident as this description proceeds. Common tripper bar 55 is rotatable in a clockwise direction upon the occurrence of predetermined circuit conditions to release the cooperative engagement of members 53, 54 and 66, 67. That is, upon the occurrence of a persisting fault the free end of bimetal 21 deflects to the right with adjusting screw 68 engaging tripper bar extension 69. Upon the occurrence of a severe overload, armature 70 will be attracted by magnet 19 with adjusting screw 71 moving to the left to engage tripper bar extension 72.

Pins 77 extending outwardly from the arms of cradle 60 pivotally mount cradle 60 to frame 42. Toggle linkage 62, 63 as well as spring means 64, 65 are mounted between the arms of cradle 60. It is to be noted that each of the toggle links 62, 63 are split members.

Lower toggle link 63 is connected at one end to movable contact arm 24 at pin 31 while the other end is connected to pin 73 which forms the knee of toggle linkage 62, 63. Upper toggle link 62 is connected at one end to pin 73 and at the other end is pivotally connected at 74 to cradle '60. The upper ends of springs 64, 65 are secured to operating member 45 while the lower ends of springs 64, 65 are secured to plate 75 which is pivotally mounted to pin 73. Collars 76 position links 62, 63 axiall-y on pin 73.

Springs 64, 65 are tension members so it is readily seen that they bias cradle 60 counterclockwise about pins 77, bias operating member 45 against bushings 101 mounted upon pins 43, and bias contacts 25, 26 both into and out of engagement depending upon the position of toggle knee 73.

Circuit breaker 10 is manually operated between its on and off positions by means of handle 49. With the circuit breaker 10 in the closed position of FIGURE 2 movement of handle 49 to the right moves the upper end of springs 64, 65 to the right. At such time as the force of springs 64, 65 acts along a line positioned to the right of the line joining knee 73 and pivot 74, knee 73 will be drawn overcenter to the right and contacts 25, 26 will be disengaged with a snap action. By moving handle 49 in the opposite direction the reverse operation takes place with the contacts being brought into engagement with a snap action. Surface of cradle 60 is positioned at an inclination of approximately 45 with respect to the direction of travel of pin 73 just prior to its stoppage. Inclined surface 85 causes .a downward component of force to be exerted on contact arm holder 32 with this component of force being absorbed by contact arm biasing spring 37.

Hereinbefore, there has been described the construction of the circuit breaker 10. The construction is such that assembly is considerably simplified over the assembly required for prior art circuit breakers of similar construction. That is, the contact operating mechanism 30 is assembled by first mounting all of the elements in place upon frame 42 except for bushings 101 and snap ring retainers 162.

Because of this, initially handle extension 45 is in the position of FIGURE 5 with respect to pivot pins 43. In this position contact operating springs 64, 65 are in relaxed condition. Thereafter, springs 64, 65 are loaded by moving handle extension 45 upward with respect to FIG- URE 5 relative to frame 42 so that extension 45 assumes the position of FIGURE 6 relative to pivot 43. Thereafter, bushing 141 1 is slipped over the free ends of pins 43 so as to be interposed between pins 43 and extension 45 and act as a spacer means therebetween. Handle extension 45 is then released with springs 64, 65 forcing extension 45 downward to be seated upon bushings 101 which now act as the pivot for handle extension 45. Retainers 102 disposed within grooves 103 retain bushings 101 in operative positions.

It is to be noted that handle extension 45 in the position of FIGURE 7 is raised with respect to its position of FIG- URE 5. As previously noted, with handle extension 45 in the position of FIGURE 5 springs 64, 65 are relaxed. Movement of handle 45 away from pivot 43 by the thickness of bushing 101 fully loads contact operating springs 64, 65 to the extent necessary for proper operation of circuit breaker it].

Thus, this invention provides a novel construction for a circuit breaker contact operating mechanism which enables a simplified assembly procedure to be utilized. That is, with the device of this invention loading of the contact operating springs is substantially the last step in the assembly procedure. Because of this, the elements of the operating mechanism may readily be assembled to one another and to the frame without the necessity of taking special precautions to assure that energy stored within springs will not be released to injure the worker and without the necessity of working in lined areas with members that are biased in directions so as to hinder assembly.

In the claims which follow when reference is made to operating springs which are relaxed, this is intended to cover springs that may not be completely relaxed but may be very lightly loaded to an extent where they cannot effectively function to operate the contact mechanism.

Although I have here described preferred embodiments of my novel invention, many variations and modifications will now be apparent to those skilled in the art, and I therefore prefer to be limited not by the specific disclosure herein but only by the appended claims.

I claim:

1. A method of assembling a circuit breaker operating mechanism having a contact operating spring, comprising the steps of:

securing the opposed ends of the contact operating spring to a sub-assembly with the spring mounted to an accessible portion of the sub-assembly, while in a relaxed condition; mounting the sub-assembly to a support in such a manner that the spring remains relaxed and is now located in an inaccessible region of the operating mechanism;

loading the spring from an externally accessible region of the operating mechanism to bias the circuit breaker contacts to a tripped condition;

and thereafter applying means to an externally accessible region of the operating mechanism for maintaining the spring loaded. 2. A method of assembling a circuit breaker operating mechanism having a contact operating spring, comprising the steps of:

securing the opposed ends of a contact operating spring to a pair of relatively movable members of an operating mechanism sub-assembly with the spring mounted to an accessible portion of the sub-assembly, while in a relaxed condition; mounting one of the relatively movable members of the sub-assembly to a support in such a manner that the spring remains relaxed and is now located in an inaccessible region of the operating mechanism;

loading the spring from an externally accessible region of the operating mechanism to bias the circuit breaker contacts to a tripped condition;

and thereafter applying means to an externally accessible region of the operating mechanism for maintaining the spring loaded.

3. A circuit breaker operating mechanism including a spring, support means for mounting said spring to said operating mechanism, said support means including first and second means, movable relative to each other for loading said spring, a stationary pivot for said first means including a pin and a bushing mounted upon said pin; said first and second means connected to opposite ends of said spring; said pin and said bushing being proportioned so that said spring is loaded when said said first means rests upon said bushing and said spring is substantially relaxed when said first means rest upon said pin.

4. A circuit breaker contact operating mechanism comprising a contact carrying arm, a toggle connected at one of its ends to said arm, a latchable cradle connected to the other end of toggle, a stationary pivot, an operating member mounted to said pivot and operatively connected to said toggle, an operating spring means connected between said operating member and said toggle at the knee thereof; said member being operable to selectively position said spring means whereby the later selectively moves said contact arm between a contact engaged position and a contact disengaged position when said cradle is latched; said pivot comprising a pin and a bushing mounted upon said pin; said pin and said bushng being proportioned so that said spring means is loaded when said operating member rests upon said bushing and said spring means is subtantially relaxed when said operating member rests upon said pin.

5. The mechanism of claim 4 in which the spring means comprises a coiled tension spring.

6. A circuit breaker contact operating mechanism comprising a contact carrying arm for movement into or out of engagement with a cooperating contact, a toggle connected at one of its ends to said arm, a latchable cradle connected to the other end of said toggle, a stationary pivot, an operating member mounted to said pivot, an operating spring means connected between said operating member and said toggle at the knee thereof; said member being operable to selectively position said spring means whereby the latter selectively moves said contact arm between a contact engaged position and a contact disengaged position when said cradle is latched; said pivot comprising a pin, and spacer means mounted upon said pin, said spacer means positioned intermediate said pin and the cooperating portion of said operating member in engagement with said pivot; said pin and spacer means proportioned so that said spring is loaded when said cooperating portion rests on said spacer means, and said spring means is substantially relaxed when said cooperating portion rests upon said pin; said spacer means being accessible external to said operating mechanism to permit spring loading subsequent to assembly of said operating mechanism.

References Cited by the Examiner UNITED STATES PATENTS 1,944,185 1/1934 Langer 267-1 2,065,357 12/1936 "on Hoorn 200-116 2,145,704 1/1939 Wood 2671 2,631,208 3/1953 Page 200-88 2,657,292 10/1953 Edmunds 200-88 2,685,009 7/1954 Cole 20088 3,012,118 12/1961 Edmunds 200-88 BERNARD A. GILHEANY, Primary Examiner. 

3. A CIRCUIT BREAKER OPERATING MECHANISM INCLUDING A SPRING, SUPPORT MEANS FOR MOUNTING SAID SPRING TO SAID OPERATING MECHANISM, SAID SUPPORT MEANS INCLUDING FIRST AND SECOND MEANS, MOVABLE RELATIVE TO EACH OTHER FOR LOADING SAID SPRING, A STATIONARY PIVOT FOR SAID FIRST MEANS INCLUDING A PIN AND A BUSHING MOUNTED UPON SAID PIN; SAID FIRST AND SECOND MEANS CONNECTED TO OPPOSITE ENDS OF SAID SPRING; SAID PIN AND SAID BUSHING BEING PROPORTIONED SO THAT SAID SPRING IS LOADED WHEN SAID SAID FIRST MEANS RESTS UPON SAID BUSHING AND SAID SPRING IS SUBSTANTIALLY RELAXED WHEN SAID FIRST MEANS REST UPON SAID PIN. 